Reciprocating pistons (oscillators) are used in a great variety of fluid flow machinery, and are well known in the art. Two types of oscillators are employed, namely, "zero net fluid flow", in which there is no throughflow of fluid and the fluid, on which the oscillator acts, only undergoes pressure fluctuations as it interacts with the oscillatory member, and the "net fluid flow", in which fluid flows through the oscillator by means of induction and delivery valves and undergoes either fluid compression/pumping action, or fluid expansion.
Two types of pressure fluid oscillators are employed in each case, and the present invention is directed to both these types. They are the "displacement oscillators", which serve only as recoil or bouncing oscillators driven by a pulsating fluid pressure, and "power oscillators", which convert power from pulsating fluid pressure to mechanical or electric power, or vice versa, via the oscillatory member.